For those of you with a short attention span, here is the finished MK I Multicart in action.

Whoa! That's so cool! How do I make the SC-3000 Survivors MK I Multicart for myself?

This project is (reasonably) simple to build. You can do it with a few off the shelf components and fit it inside
an existing SC-3000 or SG-1000 cartridge case.

We're going to take an old SC-3000 game cartridge, remove the existing ROM
that the game is stored on, and replace it with a much larger EPROM
which can hold 32 games plus some extra wires to a DIP switch
to let you choose which of those 32 games to run. That's it. Sounds simple, eh?

The main reason why this build is so easy is that we are going to use an external EPROM programmer. That means we don't need
any hardware to interface with a PC, and we don't need custom software to load the new games onto our cart.

Once upon a time this would have been very expensive, but right now you can buy a cheap EPROM programmer on eBay
for $45 - $50USD including shipping, and a large 8MBit / 1MB EPROM for $7-$10 including shipping. And you can get
a UV eraser (for when you want to change your games selection) for about $20USD on eBay including shipping.
Those are the most expensive part of the build - everything else is cheap and easy to find.
And the EPROM Programmer may come in handy for some later projects too :)

You will need some basic soldering skills. And if you don't have basic soldering skills, then this is the perfect time to learn!
Some of the soldering work is a bit fiddly, and you may end up cursing a couple of times. But once you've had a bit of
practice you will be able to build one of these real quick.

Disclaimer:

We take no responsibility for any damage caused to you, your property, your favourite cat, dog, pet bird, Uncle Bob,
or Aunt May by the use or misuse of the information contained in the SC-3000 Survivors Multicart Project. We've done
our best to come up with a project that is relatively safe and simple, but everything you do is at your own risk.

Overview - How / Why the Multicart works

How a SC-3000 games cartridge works
Bank Switching / Memory Mapping / Paging
How the SC-3000 Mk I Multicart Paging works

Home computers like the SC-3000 are simple enough that you can build one in your own garage. The SC-3000 Survivors
MkI Multicart uses some old skool
tricks and parts that have been around since the dawn of home computing. And with a bit of luck you will even be able
to understand how and why it works.

How a SC-3000 games cartridge works

Yamato Circuit Board

SC-3000 Games cartridges are very simple - they don't have much in them. Check out the following picture of a Yamato games cart.

There are only three components on that board. The 4.7uF electrolytic capacitor is designed to smooth out any major fluctuations
in the power supply from the SC-3000. The 0.1uF ceramic or polyester capacitor is designed to decouple the ROM and smooth out
any noise in the system caused by the rapidly changing voltage states at the ROM input and output pins.

The big black thing in the middle of the circuit board is the ROM
chip that contains all the program code and screen data for the game. Almost all the SC-3000 games carts contain a single 28 pin
ROM chip that holds either 16KB or 32KB.

The sole purpose of that circuit board is to supply that ROM chip with power and to connect the address and data lines
from the Z80A CPU to the pins on the ROM.

32KB ROM Pinout (256KBit)

The original 256KBit / 32KB ROM has 28 pins in total (see diagram). 15 of these are address pins - A0 to A14.
That allows the SC-3000 to address all of the lower 32KB of memory space (0000 to 7FFF) in the ROM (as 2^15 = 32,768).

For example, say the computer needs to access the memory stored in position 14,297. That is 011011111011001 in binary.
So the CPU just turns the voltage to the corresponding pins on or off. ie.

Bank Switching / Memory Mapping / Paging

The Z80A is an 8 bit processor and only has a 16 bit address range. That means it can never directly address more than
64KB of memory. That wasn't a problem for the SC-3000 as all its games cartridges were 32KB or smaller.
(Well, mostly anyway - there are a couple of ROM dumps floating around that are 40KB, but there are generally
smaller versions of those games available, so we will ignore those). So the games carts usually just had a
single ROM chip which was hard wired into the
lower 32KB of memory, and the SC-3000 had 2KB of RAM located at the 48KB mark for storing temporary calculation results.

But newer 8 bit systems like the NES, the Sega Master System, Commodore C128, Amstrad CPC 6128 etc. soon needed more storage.
They solved that problem with Bank Switching.
Those systems could write out special instructions to a paging chip that would 'swap' part of the memory that the
processor was connected to out to another portion of the ROM or RAM. Many SMS games, especially the later ones,
required significantly more than 64KB to store all the game graphics and sound data, and each of these carts had a
built in paging chip.

How the SC-3000 Mk I Survivors Multicart Paging works

The SC-3000 Survivors Mk I Multicart uses a very simple paging design (simpler than the SMS carts).
We just swap out the bottom 32KB of memory space (0000 to 7FFF) to a different portion of a large 8MBit (1MB)
EPROM. The 8MBit EPROM is 32 times larger than the original
256KBit / 32KB ROM, so we can fit 32 games on it. And because we are only paging or swapping out the lower 32KB of memory,
we don't need to make any changes to the RAM access which is always in the top 32KB of memory from 8000 to FFFF.

8MBit / 1MB EPROM Pinout

Our new 8MBit / 1MB EPROM has 32 pins in total. 20 of these are address pins - A0 to A19 (see diagram).

Now, see how the layout of the bottom 26 pins is identical to the original ROM? That lets the Sega control the bottom 15
address pins A0 to A14 as normal, but we control the +5v or 0v / GND signal to the A15 to A19 pins with a DIP switch.

The DIP switch breaks the EPROM up into 32 distinct 32KB blocks and lets us map the base address 0000 to an arbitrary
block within the 8MBit EPROM. One side of the DIP switches is connected to +5v, and the other side is connected
to A15 to A19 and a pull down resistor network to force the logic level to GND or 0 when the DIP switches are open.
When they are closed, it forces +5v or logic 1 at the relevant pin.

That's pretty much it. The only other changes we had to make to the original circuit board layout were to cut a
couple of circuit lines that forced the A15 and A17 pins to +5v.

I won't say much about these. If you know what they are, then you probably have most of them already. If you don't
know what they are, then click the links for more information and you can get them at any Electronics or Hobby store.

Skills - Soldering

Soldering is pretty easy to do once you've had a bit of practice. There are loads of good soldering tutorials
around on the net, and I'm probably not the best person to teach you anyway :)

Components

Yamato Cart

Donor cart

Free - just choose one you don't mind destroying :)

Cat 5 Ethernet Cable

Wire (eg. Cat 5 cable)

I just used Cat 5 Ethernet cable for the wiring in this project. You don't need much - 1 meter of cable is plenty.
If you have an old cable hanging around then you can just cut the connector off the end and strip the individual
wires out. Or you can buy some from a electronics store for around $1 / meter.

There is just one thing to be aware of - single core vs stranded wires. Single core wires are made from one
piece of copper and stranded wires have several very thin pieces of copper twisted together. Both will work,
but stranded wires are better suited to this project because they are more flexible than single core wires.
You have to squish the DIP switch into place at the end when you assemble the cartridge. This is harder
with single core wire, and you are more likely to accidentally break one of the joints you have so
carefully soldered onto your socket. However you do need to take care that the strands don't come loose
and cause a short circuit when you are soldering.

6 Position slider style DIP switch

6 position slider style DIP switch - $3

A DIP switch is just several little on / off switches joined together in a little plastic package.
We are going to use the DIP switch to supply either +5v (on) or 0v / GND (off) to the top 5 address pins on our
new, bigger EPROM. You only need a 5 position DIP switch, but I used a 6 position DIP switch because I might use
that spare switch for something in a later project.

There are 3 main types of DIP switches: Slider, Piano, and Rocker. You want one that is easy to shift with
your fingers. I used a slider style switch. A Rocker style switch could work well too, but you may need to
glue the switch in place so you don't push it back inside the cartridge case when you change the switch positions.
I would not use a Piano style switch - too fiddly. And do NOT get a DIP switch with recessed switches as you
will need a needle or small screw driver to change the switch positions.

ST Micro 27C801 8MBit EPROM

8MBit / 1MByte UV Erasable EPROM

We are going to replace the existing ROM with an 8 Megabit (1 Megabyte) EPROM http://en.wikipedia.org/wiki/EPROM.

Look on eBay for 27C801 ST Micro EPROMs. These are going $6-$8 USD plus shipping on eBay. You can get two for $16 including shipping.
Or $10 including shipping.

Note - you want the UV erasable EPROMs in a 32 pin ceramic DIP package. These are the ones with a little quartz crystal window
that can be erased and reused. You can also get OTP (One Time Programmable) PROMs. Internally they are identical,
but they come in a solid plastic package without the quartz window, so you can only write to them once.

32 pin DIL / DIP Socket

32 pin DIL / DIP Socket

These are known as DIL (dual in line) sockets or DIP (dual inline package) sockets.

The socket makes it easy to insert or remove our EPROM whenever we want. I would buy a couple if I were you so you have a spare.

Important: Take a careful look at the style of 32 pin socket I have used. See how it has round pin holes?
See how the round holder extends below the plastic frame? You're going to need one like that so you can trim some of the
pins and solder wires to them without touching the circuit board below.

Do NOT use this type of Socket

Here is an example of a socket you do NOT want to use. These have little spring connectors instead of round holes.
The problem is that the pins don't extend very far below the plastic socket body. So if you use one of these you will
probably find it hard or impossible to trim the pins, solder wires to them, and still get the
cartridge case to shut afterwards.

Top853 Universal Programmer

EPROM Programmer

This is a cheap Top853 Universal Programmer I bought off eBay for $35 USD + $12USD shipping. It works really well. The software
supposedly runs on Vista and Windows 7, although I had to use XP because it doesn't seem to have 64 bit drivers for my 64 bit Vista OS.

UV Eraser

UV Eraser

Just buy yourself a cheap 'N nasty UV eraser like this off eBay for around $20. All you have to do is pop your EPROM
in the eraser and set the timer to about 10-15 minutes. Then your EPROM is blank and ready for writing again.

22K Ohm SIL Resistor Network

22K Ohm SIL Resistor Network $2

This ensures that pins A15 to A19 on our EPROM get a good clean 0v / GND signal when the DIP switches are open.

Spare 0.1uF ceramic capacitor, 16v to 50v - 50 cents

ROM images - Free

Just type sc3000 sg1000 roms into google and have a good hunt around :)

Build Sequence Checklist

Here's your quick summary that makes the build sound really easy. You should check this off as you go.

Remove the 100nF (0.1uF) capacitor from the board
Save it for re-use later unless you have a new one to replace it with.

Put tape down over the circuit lines that will run underneath your new 32 pin socket.
This is optional, but it may save you a short circuit later.

Prepare 32 Pin Socket - Trim pins
The circuit board was only designed to hold a 28 pin IC, and we are going to attach a 32 pin IC.
Trim those extra 4 pins (A16, A18, A19, VCC) to fit your PCB.

Prepare 32 pin socket - attach wires to socket
Solder 5 x 8cm flexi-core wires to socket pins A15, A16, A17, A18, A19. Top two pin wires point towards
top of circuit board, next two point left / right. Be careful not to short anything out.

Prepare DIP switch - attach +5v wire
Solder a single 10cm flexi-core wire to all pins on the OFF side of the DIP switch

Prepare DIP switch - attach network resistor
Solder 22KOhm Network Resistor to all the pins on the ON side of the DIP switch. Make sure that the common pin
on the Network Resistor (marked with a dot) is off to the side.

Attach Socket wires to DIP switch
Attach 32 pin socket to the Network Resistor (ON) side of the DIP switch. Trim wires to size as you go.
A19 goes to DIP1, A18 to DIP2, A17 to DIP3, A16 to DIP4, A15 to DIP5.

Attach 0.1uF to DIP switch and Network Resistor
Attach 100nF capacitor we removed earlier (or use a new one) between GND pin on network resistor and the
middle of common 5v line across the OFF side of dip switch

Solder the 32 pin socket to circuit board
Solder the 32 pin socket (plus attached wires) onto the circuit board.
Remember you have to elevate it *just* enough so that you don't get a short circuit between the last 4 pins on socket and
the circuit lines running underneath. But if you elevate it too much you won't be able to screw the cartridge
case back together. It is a tight fit once the EPROM is in place :)

Solder +5v and GND wires from DIP switch to underside of PCB
Solder +5v wire from OFF side of dip switch to +5v / VCC on underside of circuit board. Solder GND wire from common
pin on Network Resistor to GND on underside of circuit board.

Cut two lines on circuit board
The original circuit board forces pins A15 / A17 to +5v, but we want to control them from the DIP switch.

Test all connections with multimeter
It is important to do this thoroughly. It will save you hassle later, and should stop you from frying your SC-3000
if you have accidentally shorted something out.

Insert the new 8MBit EPROM into socket

Test the FIRST Game on Multicart
Set all DIP switches to the OFF position. Plug the Mk I Multicart into the SC-3000 and turn it on.
You should see the first game from your cart on screen. It should be the first game listed on the
label you created earlier.

Test the LAST Game on Multicart
Turn the SC-3000 off. Set all the DIP switches to ON. Turn the SC-3000 on. You should see the last game from your
label on screen.

Test a few other Games on Multicart
Turn Sega off. Choose a game from your Multicart label. Set the DIP switches to the positions for that game.
Turn Sega back on. Check you get the game you were expecting. Repeat a few times.

Mark and cut hole in plastic case for DIP switch

Reassemble Cartridge Shell and apply Label

Done - Go Play some cool games
You now have your very own SC-3000 Survivors Mk I Multicart. Go have some fun - you've earned it.

Detailed Build and Testing Instructions

Remember - this is what we are trying to build. We're just going to remove the ROM from an existing cartridge and attach a new
larger EPROM instead plus a few extra control wires running to a DIP switch. That's it. Simple :)

1. Choose your Donor cart

This is the one step where you might need a bit of help from us because if you choose a cart with a different circuit board
layout then you may need a couple of minor modifications to the design. You can use almost any SC-3000 or SG-1000 cart,
but some are better suited than others.

The donor cart for this project was Yamato. I have seen the same circuit board layout used for N-SUB, Sinbad Mystery,
Star Jacker, and Congo Bongo. Look for a cart with all 44 pins on the cartridge edge connector and you have a good
chance of finding this board (some have several pins missing on the B side or ROM side). Here are a variety
of games cart circuit board layouts.

Any 32KB games cart *should* be fine. Most of the 16KB carts are ok too. But Sega used several different circuit boards
for their carts, and you can't guarantee what you will find inside when you open up the cart as the local distributors
in each country sometimes hacked the boards together themselves. Do NOT use the
Champion Tennis cart (8KB ROM).

Side B - Top of Yamato PCB (component side)

If you can't find the exact same circuit board layout, then send us pictures of both sides of the circuit board you want to
use and we may be able to make suggestions. Just make sure we can see all the circuit board lines clearly. In any case
you should definitely read the "How it works" section because it is actually fairly simple to figure out what to change
once you understand how the Multicart works.

Side A - rear of Yamato PCB (solder side)

A Basic IIIA or IIIB cart will work just fine, but I highly recommend you use a games cart instead as it is a much
simpler build. There is less room on the circuit board and inside the case, you will have to move a couple of capacitors,
and there are plenty of other components to fry on the board. (See failed Mk 0 Multicart)

Note: You can NOT run Basic on the Multicart unless you use a Basic IIIA or IIIB cart because Basic requires the
cartridge to have 16KB or 32KB of RAM on board.

2. Check donor cart AND SC-3000 both work BEFORE we start

Plug your donor cart into your SC-3000 to both it and the cart are working before we start. I wasted several days
building my first Multicart on an empty Basic IIIB shell only to discover that it didn't work. I still don't know
whether it was bust before I started, or whether I fried one of the components during the build.
In any case, I could have saved myself a lot of pain by checking first.

3. Open your Donor Cart

Just unscrew the two Phillips head screws hiding under the sticker on the top of the cart and it should pop open.

Remember basic anti-static precautions You can probably get away with just touching a grounded metal object like
a window frame before working with electronic components. That's all I've done for years. But for this project I bought
myself an anti-static wristband off eBay - it only cost $1 with free shipping. I don't know if it makes a difference or not,
but it makes me feel better :)

4. Remove the existing ROM

The thing you need most for this step is patience. At first you think you'll never get it off. But if you keep at it
you will get it out in about 45-60 minutes. Or if you are willing to cut the ROM off then you can get the circuit board
all cleaned up in around 15-20 minutes.

If you don't care about the original ROM, then you can cut the pins and quickly flick them out with your soldering
iron / long nose pliers. Just don't cut too close to the board so you have something to grab. This is the quickest
approach and has the lowest chance of you damaging your circuit board by overheating it. (If it gets too hot then the
copper trace may start to lift of the board - that's bad. This technique is quicker, so the board contacts will be cooler.)

I wanted to save the original Yamato ROM to read it later just for interest. So I used a solder sucker to quickly suck up
as much solder as possible, then the desoldering braid to get rid of the bits hiding down beside the pins.
I then went around all the pins one by one they until started to come free. You then gently lever the ROM out with a screw driver,
or IC tweezers. Just take care not to use too much pressure on the circuit board when you're trying to get the ROM out.

Here is an excellent tutorial I found on YouTube demonstrating how to cut an IC off your circuit board and how to clean up the
holes with solder, solder sucker, and desoldering braid. If you haven't done this before then I highly recommend you watch
the video in full - I found it very helpful.

More Desoldering Resources:

Desoldering Tools

You don't need one of these for this project, but they sure make the job quicker.

Commercial Desoldering tools have a vacuum tube built
around a heating element tip. So all you have to do is heat the joint and start the vacuum. I wish :)

5. Board Layout / Hole and Pin Labels

Side B (component side) - original Yamato ROM removed

Now that we have the ROM out, let's look at the labels for the holes on the board. I am going to use these labels during the
rest of the build so use this for reference later on. And just remember - if you flip the board over, the pins are all
reversed and it is easy to look at the wrong hole. You'll see what I mean once you have the board in your hand and turn
it over a couple of times.

In our How it Works section we showed you how the original ROM has only 28 pins (link) and our new 8MBit ROM has 32 pins (link).
I have overlaid the 32 pin layout of the new EPROM onto the circuit board (click the picture to enlarge).

Side A (solder side) - Original Yamato ROM removed

I have also labelled the +5v feed (cartridge pins B01, B02) and the GND or 0v feed (cartridge pins B21, B22) from the
cartridge connector. See how the +5v line runs up the left hand side of the front of the board (Side B) then jumps to
the back of the board (Side A)? See how the GND line runs up the right side and along the bottom of Side B then jumps
to the back of the board (Side A). You need to know where these are later on for testing purposes.

6. Remove the 0.1uF (100nF) capacitor from the board

Just heat up the solder and use your solder sucker or desoldering braid to quickly remove most of the solder.
Then gently pull on the capacitor whilst applying a little heat to the remaining solder and it should pop out.
You will need to save this for re-use later unless you have a spare 0.1uF (100nF) capacitor.

7. Put tape over the circuit lines

click to enlarge

Put tape down over the circuit lines that will run underneath your new 32 pin socket. This is optional, but it may
save you a short circuit later.

8. Prepare 32 Pin Socket - Trim pins

Remember to find the end of the socket with the notch. This always goes to the top. This is just a little
visual reminder to make sure you always stick your EPROM in the right way up as the EPROM has a corresponding notch at one end.

The circuit board was only designed to hold a 28 pin IC, and we are going to attach a 32 pin IC. So we have to make those
last 4 pins fit somehow (A16, A18, A19, VCC).

click to enlarge

This step will vary a bit depending on the exact layout of the board you've used as a donor.

Check out the A16, A18, A19, and VCC pins on the photo to the right.

It just so happens that my new VCC pin fits perfectly into an existing hole on this circuit board which is attached
to the +5v line. Sweet - no changes required. Your board may be different and you may need to trim this one also
and run a short wire to a +5v feed.

The A16 and A18 pins will be sitting directly over the top of those circuit lines we just taped up, so they are trimmed nice and tight.

I decided to bend the A19 pin out instead of trimming it as that doesn't have any circuit lines under it. If I was
doing the build again, I would trim it flush just like A16 and A18 because the extra height required by the time
I attached a wire to it and some solder meant that the Yamato cartridge case doesn't *quite* shut properly. Dammit :)

9. Prepare 32 pin socket - attach wires to socket

Don't flex wires too much or they may break off - hard to resolder later

Point in different directions

Top two pin wires point towards top of circuit board, next two point left / right.

10. Prepare DIP switch - attach +5v wire

click to enlarge

Figure out DIP switch orientation. Hopefully you chose a slider style dip switch and hopefully it is nicely
labelled with ON / OFF, and numbers for each switch. See how my one has each switch labelled as 1,2,3,4,5,6?
I'm going to call those DIP1, DIP2, DIP3, DIP4, DIP5, DIP6 from now on.

click to enlarge

Take a single 10cm flexi-core wire and strip the last 1-2cm. Loop this through all the pins on the OFF side of DIP
switch array so the bare wire is touching all 6 pins.

Then solder the wire to all 6 pins

11. Prepare DIP switch - attach resistor network

click to enlarge

Solder 22K Ohm resistor network to all the pins on the ON side of DIP switch array. Make sure that common pin on the
Resistor Network (marked by a dot) is clear to the side.

Why do we do this? We are using this as a
Pull Down resistor. This ensures that we get a nice clean GND or 0v when the DIP switches are in the OFF position.

12. Attach Socket wires to DIP switch

click to enlarge

Attach the wires from the 32 pin socket to the Network Resistor (ON) side of the DIP switch.
A19 goes to DIP1, A18 to DIP2, A17 to DIP3, A16 to DIP4, A15 to DIP5.

click to enlarge

Think about where the DIP switch is going to poke out of the case (see step 22 LINK) and trim the wires to size as
you go leaving only a couple of cm of slack. I chose to poke my DIP switch out the top of the case (see
following picture of completed multicart), but you might prefer the sides.

13. Attach 0.1uF to DIP switch and Network Resistor

click to enlarge

Add the 100 nF (0.1uF) capacitor we removed earlier between the GND pin of network resistor and the +5v side of DIP switch.
You can see I have used a new 0.1uF ceramic capacitor instead of the original one.

14. Solder the 32 pin socket to circuit board

Remember you have to elevate it *just* enough so that you don't get a short circuit between the last 4 pins on socket
and the circuit lines running underneath. But if you elevate it too much you won't be able to screw the cartridge
case back together. It is a tight fit once the EPROM is in place :)

15. Solder +5v and GND wires from DIP switch to underside of PCB

Your board should look something like this

This step will vary a little depending on the exact circuit board you chose as your donor cart.

Solder +5v wire from OFF side of dip switch to +5v / VCC on underside of circuit board

Solder GND wire from common pin on Network Resistor to GND on underside of circuit board.

16. Cut two lines on circuit board

Line to cut - Front

Line to cut - Front

The original circuit board forces pins A15 / A17 to +5v, but we want to control them from the DIP switch.
So we have to cut the lines on the circuit board that join A15 / A17 to +5v. This step may vary depending on
which circuit board you chose as your donor, but the chances are those two pins will still be forced to +5v and you
will need to cut something.

Use a sharp craft knife to cut the line a few times in one place. You then may then want to use a small screwdriver to
lever up a tiny bit of the circuit trace just to make sure.

Important: Try really hard not to slip. You don't want to cut or damage anything else on the circuit board, or your fingers :)

Line to cut - Rear

Line to cut - Rear

17. Test all connections with multi-meter

It is important to do this thoroughly. It will save you hassle later, and should stop you from frying your SC-3000
if you have accidentally shorted something out.

Watch the following video on how to do it. That is easier than trying to explain how to test everything.

Here's the checklist I follow in the video:

Set all 6 DIP switches to OFF

Make sure no shorts between +5v and GND

Check for continuity between VCC and +5v

Check for 22KOhm resistance between A15 to A19 and GND

Set all 6 DIP switches to ON

Check for continuity between A15 to A19 and +5v

Advanced Troubleshooting Tips

Check out the last bit of the video. Also Pinout chart for the cartridge connector and labelled image?

18. Insert the new 8MBit EPROM into socket

Insert your new 8MBit EPROM containing your chosen 32 games into the socket. That sounds simple - and it is.
But it can also take a bit of practice. Check out the video clip below for some hints and tips.

Your completed board plus EPROM should look something like this

The most important thing to do is to make sure that your pins line up with the socket before you try to push it in.

The socket is likely to be a bit stiff to start with and the EPROM pins are unlikely to line up without some adjustment.
Watch the video - I managed to stuff that up on camera for you and bend a pin :)
I fixed it though.

19. Test the FIRST Game on Multicart

Ok, hopefully your Mk I Multicart is ready to rock now. So now is a good time to remind you about our
disclaimer before you
plug it into your SC-3000 :)

Important: Always turn the SC-3000 power off BEFORE changing the DIP switch positions. Failure to do so will result in
unpredictable behaviour at best and may damage either the Multicart or your SC-3000.

Set all DIP switches to the OFF position.

Plug the Mk I Multicart into the SC-3000 and turn it on. You should see the first game from your cart on screen.
It should be the first game listed on the label you created earlier.

Troubleshooting Tips:

If you get a game, but just not the one you expected, then you've either created the ROM image incorrectly,
or you have mixed up the wiring from A15 to A19 to the DIP switch. Try to figure out which :)

If you don't get anything loading on screen, then turn the SC-3000 off, remove the cart and gently reinsert.
Turn power back on again. Repeat a couple of times.

Try a known good cart and make sure that still works.

Consider cleaning your SC-3000 cartridge port. This is simple to do and makes a big difference to how easy it
is to plug a cart into your Sega.

If your cartridge port is really dirty, you might need the
white T-Shirt cleaning trick.
Just remember that water and electricity do NOT mix, so watch the video in full.

Look at the screen display and listen to the sound your TV is making. Hopefully it just looks and sounds like a badly
inserted cart. If you've spent any time with SC-3000s then you know what I'm talking about :) What you don't want is
something that feels quite different - eg. A hum or moving interference pattern on screen instead of a reasonably
static dark picture. That might indicate some sort of subtle wiring fault or faulty bypass capacitor.
Go back and re-check all the previous instructions, testing, and wiring.

20. Test the LAST Game on Multicart

Turn the SC-3000 off. Set all the DIP switches to ON. Turn the SC-3000 on. You should see the last game from your
label on screen.

Troubleshooting Tips:

If you get a game, but just not the one you expected, then you've either created the ROM image incorrectly, or
you have mixed up the wiring from A15 to A19 to the DIP switch. Try to figure out which :)

If you just get a blank screen, then you may not have written to the entire ROM - check the size of your ROM image file.

21. Test a few other Games on Multicart

Turn Sega off. Choose a game from your Multicart label. Set the DIP switches to the positions for that game.
Turn Sega back on. Check you get the game you were expecting. Repeat a few times with different games.

22. Mark and cut hole in plastic case for DIP switch

You can see I chose to poke the DIP switch out the top of the case. This keeps it clear of the new label on the
front of the cart and clear of the circuit board. Plus most of the wires from the circuit board are a similar
length and don't have to bend much which feels like a good design choice (although probably doesn't make any difference).
Feel free to poke it out somewhere else - just think carefully before you start cutting and make sure you will be able
to shut the case afterwards.

You can glue the DIP switch in place if you want, but I chose not to. I want to be able to easily open the cart again
later when I want to update the EPROM. The tension in the wires actually seems to hold it in place quite well.
If I was going to glue it, then I would only glue the DIP switch to the bottom half of the case.

you may need to trim the reinforcing ribbing on case - click to enlarge

23. Reassemble Cartridge Shell and Apply Label

The Completed SC-3000 Survivors Mk I Multicart

Tape the label we printed out in step 1 to the front of the multicart showing all the games and DIP switch positions.
Don't glue it for now because you may want to change the games stored on the EPROM later on and then you can just
print out a new label. Print out and apply sticker with cart names / dip switch positions.

24. Done - Go Play some cool games

Play those games, and rewrite the EPROM if you aren't happy with your selection. There are around 80 SC-3000 and SG-1000
carts available, so you could get yourself a couple of spare EPROMs and either make up another Multi-cart, or just swap
the EPROM in / out when you want to play a different set of games.

Preparing the EPROM image and Multicart Label

I've thoughtfully created a video showing you how to use the HxD Hex Editor to create your ROM image containing 32 SC-3000 games.

Here's a summary of the video for you

Find some SC-3000 and SG-1000 ROM images

Just go to Google and type something like

download SC 3000 ROM images SG 1000

Hunt around and you should find them. Them are often grouped with Sega Master System ROMs

Copy the 32 ROMs that you want into a new folder
You'll see why in a minute. We may have to modify some of them slightly or rename the files.

Rename your ROMs so they appear in alphabetical order

Just use Windows Explorer to rename the filenames. Some of the ROM downloads are likely to have names like
"SG1000_CongoBongo.sc" etc. Just rename to something like CongoBongo.sc

Check File Sizes. Discard any ROMs over 32KB in size and be prepared to modify any smaller than 32KB in size.
We are going to just append all these ROM images together, so they have to be exactly the right size.

Download HxD from http://www.mh-nexus.de/
Open any small ROMs in HxD to make them bigger. For each small ROM:
Ctrl-End
Edit->Insert Bytes
4000 hex bytes for 16KB ROMs, 6000 hex bytes for 8KB ROMS
Fill FF
Save File. Close File.

Do a paranoid file size check.

Highlight all 32 ROMs in Windows Explorer. Properties. There should be 32 files and 1,048,576 bytes in total.
If not, then one or more of the files is the wrong size. Check the file properties one by one. Each individual
file should now be 32,768 bytes long.

Concatenate all the files together in HxD
Extras->File Tools->Concatenate
Select all the roms, reorder as required
Output FileName First32Roms_Concat.bin

Right click on our new First32Roms_Concat.bin file. Properties. That should be 1,048,576 bytes it total.

Create the label using our handy MK I Multicart Label Word Document. Just fill in the label in alphabetical order,
or the same order you appended your ROM images together in.

We are ready to burn our image onto our new 8MBit EPROM.

Burning the EPROM

This step is going to vary depending on your particular EPROM programmer. Here are a few quick snaps from writing
with my TOP853 programmer ($47 USD on eBay including postage).

Sorry - looks like I didn't get around to taking these screenshots. But it shouldn't take you long to figure out. From memory with the Top853 the process runs something like this:

Install the TopWin6 Software (32-bit windows only)

Make sure you have a blank EPROM. If not, then stick it in the center of your cheap UV Eraser and wind the dial around to just past the number 1.
That should give it about 10-15 minutes, which seems plenty.

Insert your blank EPROM into your Programmer. Make sure you align the notch at one end of the EPROM with the pictures on your Programmer.
The Top853 has an outline of an EPROM embossed on its case to help you

Connect the TOP853 Programmer to your PC with USB cable

Run TopWin6

Run->Select Chip. Choose your chip type. I assume you're using 27C801 ST Micro EPROMs as these seem to be the most commonly available type on eBay. Menu option is?? Select EPROM from the list at the right

Choose your chip Manufacturer and specific chip. Look under the ??? Unknown Manufacturer and scroll down to the bottom. Select 27C801

Run->Read. Read chip. The data should come back as all FF. If it doesn't, then either you need to erase the EPROM or you don't have the pins lined up correctly.

File->Open. Open File. Select the .bin file you created earlier with HxD

Run->Programe Program!

See G:\Downloads\Audio_Sega\MulticartDocs\TutorialPhotos\EPROM_Screenshots

And voila! About 3 minutes later you have burned a nice new EPROM. Just remember to ground yourself before handling it

Troubleshooting your Programmer

Of course sometimes things go wrong (and the TopWin6 software is a bit twitchy - but hey, it's still good value). Here are some common problems and their resolution:

The TopWin6 software crashes or locks up during burning.
Solution A: Reboot
Solution B: Skip the

The TopWin6 progress bar stops but the programming light on the Top853 is still flashing.
Solution: Wait until it stops flashing. The programming often keeps going just fine even though the progress bar is jammed.
When the light on the Top853 stops flashing you can remove the EPROM and kill TopWin6 and the EPROM has probably burned ok. Try it out.

Write Error part way through programming.
Solution: You MUST erase the EPROM again in the UV Eraser. Next time you insert the EPROM into your Programmer, check the pins carefully
to see they are engaged correctly in the Programmer's ZIF socket.
You sometimes get a bit of oxidization on the EPROM pins. You may need to
clean them. I usually do it by just maintaining a tiny bit of pressure on the pins with the ZIF socket on the Programmer and wiggling the EPROM
left and right a bit so the EPROM pins run back and forth across the edge of the teeth on the ZIF socket.
But be very gentle if you do that :)
Reboot if the problem persists.